Sir Alex Ferguson took time out from preparing his side to face Wigan on Saturday to call upon Manchester United and Liverpool to show their "greatness" when they face each other at Anfield on Sunday week, following this week's revelations about the Hillsborough disaster. The Scot wants supporters to show mutual respect and for the minority who taunt each other over respective disasters to stop permanently.

Ferguson said: "I think what will happen for that Liverpool game, there is such a focus on it at the moment, fans will be on their best behaviour. It's a moment for those two great clubs to show why they're two great clubs. I don't anticipate any problems. There are always opportunities to show your greatness and this is another one. "It shouldn't need what's happened during the week to do that. I think Sandy Busby [son of Sir Matt, the former manager] wrote a great article about it, the two great clubs, ourselves and Liverpool, how they should understand each other's problems over the past. But the fact we're playing them after the findings we've been reading about the past couple of days does bring a focus to it.

"Both clubs have suffered tremendous fatalities through football and you would hope that maybe this is the line in the sand in terms of how supporters behave towards one another. Certainly the reputation of both clubs doesn't deserve that. You hope fans do behave themselves, support their team and that would be the end of it. We will see."

The Hillsborough Independent Panel's report cleared Liverpool fans of any blame regarding the surge that claimed 96 supporters' lives during an FA Cup semi-final at the ground in 1989. A total of 23 people, including eight United players and three club officials, were killed in 1958 when a plane carrying the team crashed on take-off at Munich.

Of his memories of football during the 1980s, Ferguson added: "The thing that sticks out in my mind at that time was those fences around the stadiums. That turned out catastrophic really. I remember us going to Derby in the time of Michael Knighton [who nearly bought United] and they had fences around the ground then. We took a massive support – before they started limiting away fans – about 10,000. Michael Knighton was walking round, shaking hands with the fans, and they were trying to climb over those fences. It was frightening.

"You think back to those fences – they were put up to stop fans going on to the pitch, if you remember. In that period there was some bad fan behaviour around the country. But it turned out it cost peoples' lives. It contributed to what happened at Hillsborough."

Ferguson is still undecided which of his goalkeepers, David de Gea or Anders Lindegaard, to select for Wigan Athletic's visit to Old Trafford on Saturday. De Gea, who cost £18.9m in the summer of 2011, was dropped when United travelled to Southampton before the international break. But Lindegaard failed to impress in United's nervy 3-2 win, to hand the Scot a selection dilemma.

Ferguson said: "I haven't made up my mind about that. I think both are capable goalkeepers – both have got lessons to learn about the English game, but one of them is going to play, I can assure you of that. Competition is always healthy for good players."

The United manager continues to have concerns over his side's defending. They have conceded five goals while scoring six in their first three matches, with the defenders Chris Smalling and Phil Jones still injured. "We're losing soft goals. We had that [same] period last year and we're going to address that, as we did last year. Because defending is every bit as important as the goals we're scoring.

"There are goals in our team, there's no question about that. But the other end has got to be balanced in terms of, do we have to score three every game to win? I don't want to go down that road. Hopefully, we keep [Rio] Ferdinand and [Nemanja] Vidic fit – that will help."Ferguson stated that Jones may be out a further fortnight on top of the eight weeks initially thought to be the period for his knee injury. Shinji Kagawa is the only other doubt for Wigan as Ferguson waits to discover if the Japanese is tired from returning from national team duty.

Against Southampton Paul Scholes's introduction as a substitute helped turn the game as United came from 2-1 down. "Paul once again came on the and it was like opening a door to another room," Ferguson said.

The manager added that Darren Fletcher may return to the United bench for a first time during his ongoing recovery from a chronic bowel condition. "I've got to make my mind up on that one. He may make the bench, looking at the options I've got, there's a possibility he could. But the important thing is he's back in the squad."

Ferguson is also content with Wayne Rooney's rehabilitation from his leg injury. "He's doing very well. The scar has healed well. He's training terrific. He's not in full training, all his work is being done with the physios."